Transfer coating



June 27, 1967 M. D. MATHIEU 3,323,190

TRANSFER COATING Filed Dec. 23, 1963 Transfer coating Paper base 22Transfer coating Release coating 20 Paper base FIG. 5

Paper base Transfer coating Recep'rar coating Paper base INVENTOR MaunceD. Marhleu BY QMM;'IM,M,

WNW ATTORNEYS United States Patent of Maine Filed Dec. 23, 1963, Ser.No. 332,868 Claims. (Cl. 117-36.1)

This application is a continuation-in-part of application Ser. No.188,987, filed Apr. 20, 1962, and application Ser. No. 272,246, filedApr. 11, 1963, both now abandoned.

This invention relates to transfer sheets such as those commonly knownin the art as carbon paper. More particularly, the invention relates totransfer sheets prepared by applying a transfer coating to a flexiblefoundation, the transfer coating comprising closely packed sphericalparticles which are bound to each other by a sufiicient amount of anon-waxy adhesive to hold the spheres together and to the flexiblefoundation, but insufficient to hold the transfer coating to thefoundation when subjected to local pressure, such as by stylus ortypewriter keys, etc. The spherical particles used according to thisinvention are advantageously prepared from organic polymer emulsions.

It has been known in the art that transfer sheets can be prepared byapplying to a flexible foundation certain coating compositions which arecharacterized by their having a waxy nature. The ability of thesetransfer sheets to transfer an image to a receiving surface in responseto local pressure is dependent upon the presence of a waxy material inthe coating on the sheets. The waxyv material is usually composed ofmixtures of waxes, oils and oily substances.

The preparation of such wax-type coatings requires specialemulsification equipment and the application thereof to a suitable baseby the hot-melt type coating equipment which requires slow coatingspeeds.

The transfer sheets prepared according to this invention avoid many ofthe disadvantages inherent in the prior art waxy papers. The transfersheets of this invention are simple and economical to prepare, and theydo not involve the preparation of any rigid emulsification of a waxymaterial or special emulsification equipment. Using conventional coatingequipment, high coating speeds can be used in the manufacture of thesetransfer sheets. The heat limitation factors, such as those which existwhen waxy substances are present, are largely avoided. These tranfsersheets, moreover, are almost completely dry and smear-proof. Theypossess a high gloss, a high scuff resistance and do not require thepresence of a solvent vehicle.

The transfer coating of this invention consists of closely packed,organic-polymer spheres bonded together and to a flexible foundation,such as paper, with an amount of adhesive sufiicient to resist ordinaryscuff and bending during normal handling, but in an amount less thanthat which would prevent release of the coating from the paper stockwhen subjected to local pressure. The transfer coating mayadvantageously contain at least about 70% by weight of hard organicpolymer spheres and, since the void space between a closely packedsystem of polymer spheres is ordinarily no more than about 27%, theamount of adhesive used should be less than that amount which wouldcompletely fill the void space, i.e., less than 27% by weight of thecoating. However, at least about 1% by weight of adhesive should berequired. The transfer sheets of this invention may be prepared bymixing together an aqueous sus ension of a suitable organic polymer;coloring matter such as a pigment or dye; and an adhesive, applying thecoating to a flexible foundation, and drying the coating thereon.

The organic polymer particles, which are in discrete, particular form,closely approximate a system of closely packed spheres. These sphereshave substantially no tendency to coalesce, that is, to deform fromtheir essentially spherical geometry under manufacturing and in-useconditions. Therefore, an emulsion polymer system is advantageouslyemployed which has a glass transition temperature higher than thehighest temperature likely to be encountered. The term glass transitionrefers to the characteristic change in polymer properties from those ofa relatively hard, brittle glassy material to those of a softer, moreflexible, rubbery substance as the temperature is raised through theglass transition temperature. In practice, a glass transitiontemperature for the polymer of about F. is normally satisfactory, sincefast-dry production conditions, even at temperatures above 140 F., donot facilitate coalescence of emulsion polymer particles having thisproperty. Also, finished product storage conditions rarely approach thistemperature. The organic polymer spheres used according to thisinvention are therefore defined by their having a glass transitiontemperature sufficiently high so that the polymer spheres are notsubstantially deformed or coalesced at the temperatures at which thetransfer sheets are prepared and stored. The use of these organicpolymer spheres form a stable coating of close-packed, uncoalesced,hard, glassy spherical particles upon their application, as an aqueousemulsion, to the base stock followed by a rapid water removal operation.

A system of close-packed, spherical particles, such as obtained by rapiddrying of a polystyrene emulsion film, contains up to about 27% voidvolume. At a typical coatweight of 3.3# per ream, a film employing apolystyrene emulsion (manufactured by the Monsanto Chemical Company,under the tradename Lytron S2, for example) is about 7 microns thickafter water removal, corresponding to about 30 layers of close-packedpolystyrene articles. It is advantageous to this invention that theaverage particle size of the emulsion particles be such that theindividual voids created as a result of spherical closepacking caneasily contain colored pigment particles. For example, use ofpolystyrene in conjunction with a copper phthalocyanine pigmentdispersion, allows formation of a coating such that about 30 copperpht'halocyanine pigment particles can be packed in each void formedamong the hard polystyrene particles.

The organic polymer spheres employed in this invention are prepared byforming an aqueous emulsion of a resinous material having a glasstransition temperature sufficiently high so that the polymer spheres arenot substantially deformed or coalesced at the temperatures at which thetransfer sheets are prepared and stored. These polymers include theso-called non-film forming thermoplastic resins as well as thermosettingresins. Although it is diflicult at times to define a definiteborderline between thermosetting resins and thermoplastic resins, theimportant point is that the resins should be non-film forming atapplication and drying temperatures and should be capable of being mixedin an aqueous medium with an adhesive and then applied to a suitablebase sheet and then dried to form a coating containing loosely boundpigmentlike resin particles, this coating being capable of beingtransferred to a receiving surface in response to local pressure. Thesepolymers are used in emulsion form, and water is the preferred medium inwhich the polymers are dispersed. It is believed that other mediumscould be employed so long as the essential relationship between thepolymer spheres and the adhesive is maintained.

Various non-film forming resins can be used according to this inventionincluding polystyrene such as marketed by Monsanto Chemical Companyunder the tradename Lystron S-2, polyacrylic resins such as thosemarketed by Rohm & Haas under the tradename Rhoplex B-85, polyvinylchloride such as marketed by the Monsanto Chemical Company under thetradename Opalon 410, polystyrene latex such as marketed by Dow ChemicalCompany under the tradename Dow Latex 5'86, polyvinyl chloride latexsuch as marketed by the Dow Chemical Company under the tradename DowLatex 700, polyvinyl chloride latex such as marketed by the Dow ChemicalCompany under the tradename Dow Latex 744-B, and the like. Other systemsof spherical particles, of course, can be used along with, or in placeof, the organic polymer spheres described above, so long as thesespherical particles function in substantially the same way as thoseprepared from the organic polymer emulsions. It is preferred that thesespherical particles have an average, diameter of about 0.05 to 0.3micron. Depending upon the particular ingredients used and the degree oftransferability desired, this range can, of course, vary. Larger polymerparticles, for example, will tend to transfer more readily than smallerparticles.

The transfer properties of the transfer sheets of this invention, asoperational products, are directly related to the strength of theadhesive bonds between the polymer spheres and to the adhesion of thecoating to the paper. In order to obtain clear, sharply-defined,transferred images, the adhesive need only bind the hard, sphericalparticles together in the vicinity of the contact points resulting fromtheir close packing. Adhesive contents beyond this are conducive to aless sensitive transfer and adhesive levels below this lead to apowdery, ill-defined image, lacking desirable handling properties of thecoated sheet.

Emulsion polymer systems can also be used as adhesives in this inventionand it is advantageous that its particles deform readily within ashort-drying time (5-15 sec.) at elevated temperatures. For example, anemulsion polymer, whose glass transition temperature is less than about140 F., preferably less than 100 F. may be used. The drying conditionsemployed in this invention can involve the use of forced hot-air drying,up to 250 F. ambient temperature, at web speeds such that waterevaporation takes place within 5 to seconds dwell-time. Under theseconditions the coated web temperature rarely rises above about 140 F.Emulsion polymers having a glass transition temperature less than about100 F., can, under these conditions, be defined as film-forming systems,that is, their properties in a coating are characteristic of the polymercontained originally in the emulsion particles, rather than of theparticles themselves. Any other well-known drying means can, of course,be used.

Preferably, the adhesive emulsion particles should be small compared tothe close-packed, spherical particles, that is a ratio in diameters, inorder to easily enter the voids between the latter and in order tomigrate to the polystyrene contact points and thus exercise theiradhesive nature. Use of appropriate concentrations of such film-formingemulsion polymers as adhesives, results in bonding between the hardpolymer sphere not unlike that obtained with use of water solubleadhesives.

The objectives of this invention can also be met by use oflarge-particle-size emulsion polymer systems as adhesives (averagediameters greater than that of the hard component), provided that thesealso fulfill the criterion of ability to flow, or coalesce, under thedrying conditions usually employed. In the situation where emulsionadhesive particles approach the size of the hard polymer spheres, theyinitially contribute to the formation of the close-packed system (i.e.,in the early stages of the water removal), as if by replacing some ofthe hard polymer spheres, but because of their deformability flow intointimate contact with, and act as a binder for, their nearest neighbors.Such emulsion polymers which form adhesive particles approaching thesize of the hard polymer spheres act in a dual role in assuming part ofthe function of an adhesive and part of the function of the organicpolymer spheres. Therefore, in a case where the adhesive particlesapproach the size of the polymer spheres and are partially coalescedduring manufacturing conditions such that only about one-half of theiradhesive properties are utilized, more adhesive can be used than whenthe adhesive particles are small in relation to the organic polymerspheres.

Various adhesives can be employed according to this invention. As statedabove, the adhesives can either be of the emulsion type or the typesoluble in aqueous systems. A combination or mixtures of the adhesivescan also be used sometimes to advantage. Representative examples ofsuitable adhesives which can be used include polyvinyl alcohol such asthat marketed by Du Pont under the tradename Elvanol 72-60, starchesincluding starch ethers and chlorinated or oxidized starches,carboxymethylcellulose, alkali soluble partial pentaerythritol ester ofwood rosin marketed by Hercules Powder Company under the trade namePentalyn 255, gelatin, polyacrylamide, vinyl acetate and copolymersthereof such as marketed by The Borden Chemical Company under thetradenames Lemas 541-10 and Polyco 678-W. Further examples includehydrocarbon resins such as methylated parafiinic chain hydrocarbonresins of petroleum origin such as marketed by Pennsylvania IndustrialChemical Corp. under the tradename Piccopale A-22, acrylic polymers suchas that available from Rohm & Haas marketed under the tradename RhoplexB-15, as well as various butadiene-styrene copolymers (40-60 ratio) suchas those marketed by The Borden Chemical Company under the tradenamesPolyco 350-W, Polyco 2414, Polyco 2419 and by Dow Chemical Company underthe tradename Dow Latex 630, acrylicvinylidene chloride copolymers suchas marketed by Rohm 8: Haas under the tradename Rhoplex R-9, as well asnatural resins such as casein. Other non-waxy adhesives can also be usedas will be apparent to those skilled in the art.

The carboxylated organic, water-soluble polymers, those which possessperiodic carboxylic acid groups along the polymer chain, such ascarboxymethylcellulose, or carboxy containing acrylic polymers areadvantageously used, preferably in the range of about 1-5 by weight, asthe adhesive and serve as a very flexible adhesive which tends to renderthe resulting transfer coating resistant to any deleterious effectswhich may be caused by storing the transfer sheets under humidatmospheric conditions.

Transfer coatings based on emulsion polymer adhesives sometimes sufferfrom deterioration in image quality and density when stored attemperatures between 60- and 140 F. and relative humidities from 40 toThis effect is due to slight flow, or creep, of the emulsion adhesiveduring storage, thereby causing an increased adhesive contact. Anincreased adhesive contact in turn results in decreased image transfersensitivity. Therefore, it is frequently advantageous to employ, inemulsion form, a socalled self-cross-linking adhesive, and adhesivewhich, by virtue of its latent chemical reactive groups, undergoes achemical cross-linking reaction among and between the adhesive particleswhen the coating, containing the emulsion, is dried under normal dryingconditions. Examples of self-cross-linking adhesives are vinyl acryliccopolymer emulsions manufactured by the National Starch and ChemicalCompany under the tradename X-Link 2833; aqueous dispersions of acryliccopolymers manufactured by the Rohm & Haas Company under the tradenameRhoplex K-3; compositions formed of 1-30% of an acrylic and/ ormethacrylic ester, a methylol compound and/or methylol-ether of(meth)acrylamide and optionally up to 20% of other copolymerizablemonomers, obtained by polymerization in emulsion or solution as morefully described in Belgian Patent No. 617,606.

Any suitable dye or coloring matter, i.e., colored pigment particles,may be mixed in with the coated composition. Examples of such dyes whichhave been advantageously employed include phthalocyanine pigment dyesuch as phthalocyanine blue marked by American Cyanamid under thetradename Calcotone D100, and carbon black such as that manufacturedunder the tradename Aquablak B by Columbia Carbon Company.Advantageously, the particle size of the solid colored pigment is lessthan about 0.5 micron.

Various compatible plasticizers may be incorporated into the coatingcomposition in small amounts as hereinafter described such as butylbenzyl phthalate, manufactured under the tradename Santicizer 160 aswell as other well-known plasticizers which will be apparent to thoseskilled in the art.

The most advantageous proportions of spherical particles to adhesiveused can be determined by routine experimentation and will varydepending upon the particular polymer and adhesive used, the rounduessof the resinous polymer spheres, and also depending upon the quantity ofcoloring material present in the coating. For example, if the adhesiveis water soluble, the amount of ad hesive used is preferably about 15%by weight, whereas, if the adhesive is in emulsion form, the amount ofadhesive used is preferably about 3-10% by weight. If the particle sizeof the organic polymer spheres is small, less adhesive will be necessarythan if the particle size is large, and if the particle sizes are moreevenly distributed, more adhesive is expected to be necessary than ifthe particle sizes are unevenly distributed. The amount of adhesive usedshould be such that together with the coloring matter, and anyadditives, the voids between the polymer spheres are not completelyfilled.

The amount of adhesive which can be used according to this inventionwould therefore normally be no greater than about 27% by Weight of thedry transfer coating, but the amount used should be sufiicient to bindthe spheres together and to the flexible foundation during normalhandling conditions. The optimum ratio in a polystyrene/polystyrene-butadiene coating has been found to be approximately 911 ona dry weight basis. The method of applying and drying the coating willalso affect the resin/ adhesive ratio. Lesser amounts of adhesive may beused under conditions of rapid drying since adhesive losses throughpenetration are not as high. When using the polystyrene resin (Lytron) astyrene-butadiene adhesive (Polyco 2414), and the phthalocyanine bluedye, the optimum ratio is found to be 12.5:l.3:0.3. When using the sameadhesive and pigment with carbon black (Aquablak B), thestyrene-butadiene content was advantageously increased to 1.5 instead of1.3.

In addition to the organic polymers, adhesives, and coloring matter,various additives may be used to improve the handling characteristics orrelease characteristics. Such additives include calcium stearate,potassium stearate, ammonium stearate, polyoxyethylene glycols,lecithin, polybutenes, polyethylene emulsions, or soft waxes. The onlyrequirement is that these additives, together with the adhesive andcoloring matter, should not completely fill the voids between theorganic polymer spheres, i.e., the organic polymer spheres shouldcomprise at least about 70% by weight of the transfer coating.

The plasticizer which may be used should only be present in smallamounts. The ratio of resin to plasticizer is advantageously about10011.25. This ratio can, however, go as high as about 100:5. The use ofplasticizers in excessive amounts will substantially interfere with thetransfer properties of the transfer sheets and must be avoided.

If desired, small amounts of semi-hard polymers up to about 5% by weightcan be used to improve the aging characteristics of the transfer sheets.These semi-hard polymers are defined by their having a glass transitiontemperature between that of the organic polymer spheres and that of theadhesive. These semi-hard polymers partially deform under manufacturingand drying conditions.

The temperature at which the coating composition is blended together, ofcourse, depends upon the particular components employed. A temperatureof about 122 F. to 140 F. may be advantageously employed in mostinstances. In drying the coating, it is desirable to supply a suitabledegree of heat in order to speed up the drying process. The onlyrequirement as to this temperature is that it should not be suificientto significantly soften the organic polymer spheres and destroy theparticle nature of the non-film forming resin which would interfere withthe transfer properties desired in the resulting sheet. Innon-plasticized polystyrene formulations, for example, dryertemperatures should be less than about 212 F. Somewhat lowertemperatures should generally be used with plasticized polystyrene sincethe softening point of the plasticized polystyrene is generally lowerthan that of the non-plasticized polystyrene. The specific dryingtemperature used with any particular formulation can be determined byroutine experimentation by those skilled in the art.

The limitation on the drying temperature is quite advantageous and oneaspect of the invention includes the step of heating of the transfercoatings to temperatures above the softening point of the organicpolymer spheres so as to deactivate or destroy the transfer propertiesof the film. The fact that the transfer properties of the film can bedestroyed by the simple expedient of heat, permits the transfer coatingsto be rendered non-transferable after the transfer coating has servedits purpose, and results in an original record (typewritten, forexample) having a nontransferable coating on the back. In addition, theimage transferred to a receptor paper can also be deactivated by heatingthe transferred image, thus improving the smudge-proofness andpermanence of the transferred image.

The coating may be applied to any suitable backing material, usuallypaper. A coating applied at a coating weight of about 2 to 4 lbs. perream 25" x 38"-500 (sheets) is desirable. This weight, however, couldvary from about '1 to 7 lbs. per ream. The coating may be applied at anysuitable solids content, generally ranging from about 10 to 40%. On anairknife coater, optimum results were obtained on a solids content inexcess of 30%. The coating may be applied at a machine speed rangingfrom about to 500 ft. per minute. Even higher machine speeds wouldprobably be suitable.

The receiving surface, which accepts the transferred image fro-m thetransfer sheets of this invention, is a surface which advantageously hasbeen treated with a receptor coating. A specially treated paper, havinga receptor coating, which can be used, is one which is coated with acomposition containing, for example, a liquid dispersion of calciumcarbonate having a relative sedimentation volume of between about 2 and6 in admixture with an adhesive, the composition having a pigment/adhesive ratio of about between 7:1 and 2: 1. Such a specially treatedreceptive paper is described more particularly in the copendingapplication of William H. Hoge and Marshall S. Barbour, Ser. No. 79,980,filed Ian. 3, 1961, now US. Patent No. 3,118,782, assigned to the sameassignee as the present application.

Thus one feature of this invention resides in the use of a combinationof two coated papers, the transfer .parer overlaying a receptor paper,wherein the transfer coating of the transfer paper is in contact withthe receptor coating of the receptor paper. Local pressure appl ed tothe transfer paper therefore results in a transferred image on thereceptor paper corresponding in area to the area at which the localpressure was applied to the transfer paper. Alternatively, a transfercoating can be applied to one side of a paper and a receptor coatingapplied to the other side and then two or more of these sheets can beplaced together so that the transfer coating of one sheet is in contactwith the receptor coating of another sheet.

The transfer sheets of this invention can also be used in conjunctionwith ordinary copy paper for reception of the image to be transferred.

A release coating between the paper base and the transfer coating can beused in this invention if desired. Such a release coating canadvantageously be used to facilitate transfer of the transfer coating toordinary copy papers or papers not having an image receptive coatingapplied thereto.

Various release coatings can be used according to this invention such asthose composed predominantly of vinyl resins. Cellulosic, polyamide,acrylic or methacrylic resins and so forth can also be used. Furtherexamples of release coatings include cellulosic resins such ashydroxylethyl cellulose polyamide, acrylic or methacrylic resins as wellas inorganic materials such as sodium silicate or colloidal silica(e.'g. silica manufactured by Monsanto Chemical Company under thetradena'me Syton). The release coating can be applied by solvent orwater techniques as will 'be apparent to those skilled in the art.Specific examples of release coatings include 20 par-ts by weightvinylidene chloride, vinyl-chloride copolymer dissolved in 80 parts byweight methylethyl ketone, parts by weight polyvinyl butyral dissolvedin 80 parts by weight ethanol and 6 parts by weight of a silica filler.

FIGS. 1-3 of the accompanying drawing are diagrammatic, enlargedrepresentations of cross-sections of three typical embodiments of thetransfer sheets of this in vention.

FIG. 1 shows a paper base 10 having a transfer coating 11 preparedaccording to the present invention adhered to the paper base. FIG. 2shows a paper base with a release coating 21 adhered thereto and thetransfer coating 22 prepared according to this invention adhered to therelease coating. FIG. 3 shows a combination of a paper base having areceptor coating 31 adhered thereto and the receptor coating contactingthe transfer coating 32 prepared according to this invention adhered tothe paper base 33. The application of pressure by means of a stylus ortypewriter key on the top or uncoated side of paper base 33 results in atransfer of the transfer coating to the receptor coating on paper base30 in areas coextensive with the application of the pressure.

In the following detailed example, which are given for illustrativepurposes only, specific embodiments of this invention are shown. Partsare by weight.

EXAMPLE 1 100 parts of a non-film forming polystyrene aqueous emulsioncontaining 50% solids (Lytron 8-2) were thoroughly mixed together with89 parts of an aqueous suspension of carbon black containing 13.2%carbon black solids, 2.5 parts of butyl benzyl phthalate, 11.2 parts ofa butadiene-styrene copolymer aqueous emulsion containing 48% copolymersolids and 120 parts of water. The copolymer contained a butadienestyrene ratio of 60. The coating composition thus prepared was thenapplied onto a base paper at a coat weight of 3 pounds per ream and thecoating dried at a temperature of 140 F. The dry transfer coatingpossessed a high gloss, high scuff resistance and was substantiallysmudge-proof. The coating on the base paper was then placed in contactwith a sheet of conventional bond white paper and pressure applied bymeans of a stylus to the backside of the paper having the transfercoating applied thereto. The coating readily transferred to the bondpaper receiving surface underlying the coating in the areas coextensivewith the applied pressure. The image transferred to the bond receivingsurface was sharp and distinct, possessed a high scuff resistance, wassubstantially smudge-proof and dry.

The coated paper, to which the stylue had been applied, was heated to atemperature above the softening point of the polystyrene particlescontained therein for a sufficient time to substantially eliminate theparticle nature of the non-film forming polystyrene pigment particles.This heating step rendered the coating non-transferable.

The bond paper, having the transferred image thereon, was heated to atemperature above the softening point of the polystyrene particles inthe same manner as the sheet having the transfer coating thereon. Theimage was completely smudge-proof and dry and possessed a high degree ofpermanence.

The coated surface of another portion of the transfer sheet preparedaccording to this example was place-d against a sheet of paper having areceptive coating thereon prepared according to Example 1 in applicationSer. No. 79,980, filed Jan. 3, 1961. When pressure was applied by meansof a stylus to the backside of the paper having transfer coatingsadhered thereto, the coating transferred event more readily to give anextremely clear and sharp image on the receptive coating of theunderlying sheet.

EXAMPLE 2 A transfer sheet was prepared in the same manner as set forthin Example 1 except that the transfer coating composition was formed bythoroughly mixing together 25 parts of a non-film forming polystyreneaqueous emulsion containing 50% solids, 1.7 parts of an aqueousalkylketene dimer containing 30% dimer solids marketed under thetradename Aquapel 380 by the Hercules Powder Company, 22.3 parts of anaqueous carbon black containing 13.2% carbon black solids, 2.8 parts ofthe same butadiene-styrene copolymer referred to in Example 1 containing48% copolymer solids and 30 parts of water.

EXAMPLE 3 A transfer sheet was prepared in the same manner as set forthin Example 1 except that the coating composition was formed bythoroughly mixing together 25 parts of a non-film forming polystyreneaqueous emulsion containing 50% solids, 2.8 parts of the samebutadienestyrene copolymer used in Example 1 containing 48% copolymersolids, 15 parts of highly dispersed phthalocyanine blue pigment pastecontaining 2% solids and 30 parts water.

EXAMPLE 4 A transfer sheet was prepared in the same manner as set forthin Example 3 except that 25.5 parts of a nonfilm forming polystyrenelatex containing 49.5% solids (Dow Latex 586) were substituted for the25 parts of the polystyrene used in Example 3.

EXAMPLE 5 A transfer sheet was prepared in the same manner as set forthin Example 3 except that 25 parts of a nonfilm forming polyvinylchloride latex containing 60% solids (Dow Latex 700) were substitutedfor 25 parts of the non-film forming polystyrene used in Example 3.

EXAMPLE 6 A transfer sheet was prepared in the same manner as set forthin Example 3 except that 33 parts of a nonfilm forming polyacrylicaqueous emulsion containing 38% solids (Rhoplex 13-85) was substitutedfor the 25 parts of the polystyrene and 21.5 parts of water was usedinstead of 30 parts of water.

EXAMPLE 7 A transfer sheet was prepared in the same manner as set forthin Example. 3 except that 25 parts of a nonfilm forming polyvinylchloride aqueous emulsion containing 50% solids (Opalon 410) weresubstituted for the 25 parts of the non-film forming polystyrene.

EXAMPLE 8 A transfer sheet was prepared in the same manner as set forthin Example 1 except that the coating composition was formed bythoroughly mixing together 55.5 parts of a polystyrene emulsioncontaining 50% solids and manufacture-d under the tradename Polyco 2306;6.2 parts of a self-cross-linking vinyl acrylic copolymer emulsion manu-9 factured by the National Starch and Chemical Company under the tradename X-Link 2833; 60.0 parts of a 2% solution of phthalocyanine blue and5 parts water.

All of the transfer sheets prepared according to the above Examples 2 to8 were observed and tested in the same manner as set forth in Example 1.The dry transfer coatings possessed a high gloss, high scuff resistanceand were substantially smudge-proof and possessed substantially the sametransfer and deactivation properties as described with respect to thetransfer sheet prepared in Example 1. The transfer sheet preparedaccording to Example 8 possessed particularly good aging properties.

In the above examples it was noted that there was a proper amount ofadhesive present in the coating compositions, i.e., there was asufiicient amount of adhesive to hold the resin particles together andadhere the coating to the paper, but the amount of adhesive wasinsuflicient to hold the coatings to the paper when subjected to thepressure such as from a stylus or a typewriter key under normaloperating conditions.

I claim:

1. The method of preparing a transfer sheet which comprises coating asuitable flexible foundation with a coating composition comprising anadmixture of a nonwaxy adhesive and an aqueous emulsion of organicpolymer spheres which have a glass transition temperature of more thanabout 140 F. and a particle size of between about 0.05 to 0.3 microns,heating the coating to a temperature which will not substantially deformthe organic polymer spheres, but which will substantially deform theadhesive so that a transfer coating is obtained which is equivalent to acoat weight of about 1 to 7 lbs. of coating per ream of paper, theorganic polymer spheres comprising at least about 70% by weight of thecoating, and the adhesive comprising between about 1-27% by Weight ofthe coating.

2. The method of claim 1 in which the flexible foundation is paper andthe coating is of a coat weight of about 24 lbs. per ream of paper.

3. The method of claim 1 in which the admixture contains a pigment.

4. A transfer sheet comprising a flexible foundation and a coatingadhered thereto, said coating comprising at least 70% by Weight ofdiscrete, non-coalesced, organic polymer spheres, and from 127% byweight of a nonwaxy adhesive which is in an amount suflicient to holdthe polymer spheres together and to the flexible foundation, butinsufficient to hold the polymer spheres to the flexible foundation whensubjected to local pressure, said organic polymer spheres having a glasstransition temperature of at least about 140 F. and having a particlesize of about 0.05 to 0.3 microns, said coating being in an amountequivalent to the amount of coating on a coated paper having from 1 to 7lbs. of coating per ream of paper.

5. The transfer sheet of claim 4 in which the flexible foundation ispaper and the coating is of a coat weight of about 2 to 4 lbs. per reamof paper.

6. The transfer sheet of claim 4 .in which the coating contains coloringmatter.

7. The transfer sheet of claim 4 in which the adhesive is a carboxylatedorganic, water-soluble polymer containing periodic carboxylic acidgroups along the polymer chain.

8. The transfer sheet of claim 4 in which the adhesive is aself-cross-linking adhesive.

9. The method of transferring images from a transfer sheet to a receptorsheet which comprises coating a base sheet with a composition comprisingan admixture of a non-waxy adhesive and an aqueous emulsion of organicpolymer spheres which have a glass transition temperature of more thanabout 140 F. and a particle size of between about 0.05 to 0.3 microns,heating the coating to a temperature which will not substantially deformthe organic polymer spheres, but which will substantially deform theadhesive so that a transfer coating is obtained which is equivalent to acoat weight of about 1 to 7 lbs. of coating per ream of paper, theorganic polymer spheres comprising at least about by Weight of thecoating, and the adhesive comprising between about 1-27% by weight ofthe coating, placing the transfer coating of the transfer sheet incontact with a receptor sheet, applying local pressure to the assemblyto effect the transfer of an image from the coating to the receptorsheet in areas coextensive with the applied pressure, and subsequentlyheating the transfer sheet to a temperature above the softening point ofthe polymer spheres for a suflicient length of time to destroy thetransfer properties of the transfer coating adhered thereto.

10. The method of transferring images from a transfer sheet to areceptor sheet which comprises coating a base sheet with a compositioncomprising an admixture of a non-Waxy adhesive and an aqueous emulsionof organic polymer spheres which have a glass transition tem perature ofmore than about F. and a particle size of between about 0.05 to 0.3microns, heating the coating to a temperature which will notsubstantially deform the organic polymer spheres, but which willsubstantially deform the adhesive so that a transfer coating is obtainedwhich is equivalent to a coat weight of about 1 to 7 lbs. of coating perream of paper, the organic polymer spheres comprising at least about 70%by weight of the coating, and the adhesive comprising between about 127%by weight of the coating, placing the transfer coating of the transfersheet in contact with a receptor sheet, applying local pressure to theassembly to effect the transfer of an image from the coating to thereceptor sheet in areas coextensive with the applied pressure, andsubsequently heating the receptor sheet having the image adhered theretoto a temperature above the softening point of the polymer spheres for asufficient length of time to render the transferred imagenon-transferable.

References Cited UNITED STATES PATENTS 1,209,222 12/1916 Statham 117-1561,374,112 4/1921 Rafsky 117-156 2,351,683 4/1944 Hughes et al 106-1482,395,992 3/1946 Clark 106-148 2,508,725 5/1950 Newman 1l7-36.72,574,439 11/1951 Seymour 260-455 2,820,717 1/1958 Newman et al 117-36.12,872,340 2/1959 Newman et al. 117-361 2,892,976 7/1959 Popielski260-455 2,970,931 5/1961 Gumbinner 117-361 3,036,924 5/1962 Newman106-145 MURRAY KATZ, Primary Examiner.

1. THE METHOD OF PREPARING A TRANSFER SHEET WHICH COMPRISES COATING ASUITABLE FLEXIBLE FOUNDATION WITH A COATING COMPOSITION COMPRISING ANADMIXTURE OF A NONWAXY ADHESIVE AND AN AQUEOUS EMULSION OF ORGANICPOLYMER SPHERES WHICH HAVE A GLAS TRANSITION TEMPERATURE OF MORE THANABOUT 140*F. AND A PARTICLE SIZE OF BETWEEN ABOUT 0.05 TO 0.3 MICRONS,HEATING THE COATING TO A TEMPERATURE WHICH WILL NOT SUBSTANTIALLY DFORMTHE ORGANIC POLYMER SPHERES, BUT WHICH WILL SUBSTANTIALLY DEFORM THEADHESIVE SO THAT A TRANSFER COATING IS OBTAINED WHICH IS EQUIVALENT T ACOAT WEIGHT OF ABOUT 1 TO 7 LBS. OF COATING PER REAM OF PAPER, THEORGANIC POLYMER SPHERES COMPRISING AT LEAST ABOUT 70% BY WEIGHT OF THECOATING, AND THE ADHESIVE COMPRISING BETWEEN ABOUT 1-27% BY WEIGHT OFTHE COATING.